Calculation of extinction cross-section of single vegetation elements placed in open resonator

The results of calculation of extinction cross — section for bodies of various shapes and electrical constants placed in open resonator are presented. Theoretical model for such structure was developed. It allowed to calculate transfer ratio, Q-factor and another characteristics of the resonator with sample. The results presented can be used for investigation of extinction cross — section for vegetation elements in millimeter wave band using open resonator.     

Measurement of the extinction cross-section of dielectric spheres using an open resonator

The measurement of the extinction cross-sections at microwave frequencies for a set of spheres made of low-loss dielectric material is reported. Measurements were carried out at Q-band using a microwave open resonator. Results are compared with calculated values derived from Mie's theory.     

Assessment of moisture content of fibres and fabrics by measurementof extinction cross-section in an open resonator

A new application of a large, computer-controlled open resonator is described. Measurement of the extinction cross-sections of samples of wet materials are recorded very quickly and continuously throughout the drying period. The measurements may be taken throughout the interval 8-12 GHz and provide a complete record of the drying process     

Measurement of extinction cross-section of single particles at 100 GHz

The extinction cross-section of single particles of dimensions comparable with the wavelength has been measured using a double resonance technique at 100 GHz. Results agree well with Mie's theory. The technique is applicable to moving particles with velocities up to a few metres per second.     

Experimental investigation for wideband perforated dielectric resonator antenna

A wideband perforated dielectric resonator antenna (PDRA) is presented. The effective permittivity of the dielectric resonator is altered by drilling holes into a circular ring lattice inside the DRA. The PDRA is equivalent of having an annular ring with lower permittivity outside the cylindrical disk, resulting in enhanced impedance bandwidth. The measured bandwidth of a prototype PDRA with relative permittivity 10.2 is 26.7% (S/sub 11/<-10 dB).     

Experimental investigation on new steerable dielectric resonator antenna

A new steerable-dielectric resonator antenna is described. It consists of a movable annulus of heterogeneous dielectric sections surrounding a cylindrical core of another dielectric. The antenna far-field radiation was found to be manipulated by changing the angular position of this ring. This antenna demonstrates resonance at ~1.2 GHz with a fractional bandwidth of 28.3% (Sn₁₁< - 10 dB), confirming an HFSS simulation of the same structure.     

Experimental investigation of microwave-optoelectronic interactionsin a microstrip ring resonator

Microwave optoelectronic mixing on a semi-insulating gallium arsenide substrate performed by monolithically integrating Schottky diode photodetectors into a microstrip ring resonator is discussed. When operated in the resistive mixing mode, a low frequency difference signal is extracted from the bias pad of the circuit. In the parametric mode, both degenerate and non-degenerate parametric amplification of an optical carrier signal takes place. The circuit shows good potential for application in wide-band fiberoptic systems     

Observation of crosspolar effects using a microwave open resonator

The occurrence of a crosspolar resonant field, generated from the interaction of a particle and the normal fundamental mode of a microwave open resonator, is reported. Results are presented for the cases where the scatterers are a short length of wire and simulated melting hailstones.     

An X-band dielectric resonator antenna using a single elliptical shaped dielectric resonator

This paper presents design evolution of a single elliptical dielectric resonator antenna to achieve wide measured impedance band-width extending from 8.26 GHz to 12.15 GHz. Design evolved from a right circular cylindrical DRA by varying the dimension along the semi-minor axis and thereby resulting in an elliptical DRA that supports near similar field distribution over the X-band. This similar field variation is achieved by tuning the eccentricity of the elliptical geometry, the feed position as well as height of the DRA. A fabricated prototype is developed and measured results agree well with that obtained from simulation. Apart from wide impedance bandwidth, the observed pattern bandwidth is also similar.     

Microwave measurements on dust, using an open resonator

The measurement at 10 GHz of the refractive index and tan ? for fine powders, sparsely distributed in the atmosphere, is reported. The realisation of a uniform density of particles within a large resonator is discussed.     

Resonant-tunnelling diode oscillator using a slot-coupled quasioptical open resonator

A resonant-tunnelling diode has oscillated at X-band frequencies in a microwave circuit consisting of a slot antenna coupled to a semiconfocal open resonator. Coupling between the open resonator and the slot oscillator improves the noise-to-carrier ratio by about 36 dB relative to that of the slot oscillator alone in the 100-200 kHz range. A circuit operating near 10 GHz has been designed as a scale model for millimetre- and submillimetre-wave applications.<>     

Experimental investigation of non-linear processes in quasi-optical resonator with paramagnetic

The following papers [1,2] are devoted to the experimental investigations of electron system in polarized nuclear target (PNT) materials and in particular in such substance as a paramagnetic complex HMBA (Cr^v). The processes of electron and nuclear system interactions in these matters were also considered [3,4]. The purpose of a present paper is the study of a nuclear system paramagnetic complex HMBA (Cr^v) in a 1,2 - propylene glycol. The super high frequency (SHF) power of saturation is changed during our experiment.     

A nonreciprocal tunable waveguide directional filter using aturnstile open gyromagnetic resonator

The 4-port waveguide directional filter is a classic network in microwave engineering. The purpose of this paper is to describe one gyromagnetic version using an open gyromagnetic resonator in a dielectric-filled cavity. A property of the circuit is that it behaves as a 4-port circulator with one direction of circulation at one split frequency of the resonator and with the other direction for the other split frequency. An insertion loss between the coupled ports below 1.50 dB and an attenuation or isolation of typically 15 dB between the decoupled ports over most of the tuning range of the filter have been achieved. Its 3-dB bandwidth is typically 65 MHz. A typical tuning range of more than 1 GHz centered at about 10.5 GHz has been separately realized for each split branch     

Compact UWB bandpass filter using ring open stub loaded multiple-mode resonator

A novel ultra-wideband (UWB) bandpass filter with a compact size, improved upper-stopband performance and reduced radiation loss has been studied and designed using a multiple-mode resonator (MMR). The MMR is formed by attaching three pairs of ring open stubs in shunt to a high impedance microstrip line. By simply adjusting the radius of the circles of the ring stubs, the resonant modes of the MMR can be roughly allocated within the 3.1?10.6 GHz UWB band while suppressing the spurious harmonics in the upper-stopband. Meanwhile, the insertion loss is higher than 20.0 dB in the upperstopband from 11.7 to 33.5 GHz in simulation. Finally, the filter is fabricated and measured. The EM-simulated and measured results are presented and excellent agreement between them is obtained.     

New technique for measurement of total scattering cross-sections using an open resonator

It is shown that, for obstacles having a ceprtain symmetry, the cross-section for absorption and scattering can be determined by measuring under prescribed conditions the Q factor of an open resonator into which the obstacle is introduced.     

Millimeter-wave permittivity measurement of deposited dielectric films using the spherical open resonator

A differential method using the spherical open resonator is developed for permittivity measurement of a thin dielectric film on an optically dense substrate. It is based on a measurement of the resonant frequency shift due to the thin film on the substrate. The accuracy of the method is demonstrated to be about 4% for a 5.6-/spl mu/m photoresist film at 142 GHz.     

Quasi-optic excitation of an open resonator

A technique and results of solution of the problem on plane-wave excitation of an open quasioptic resonator and a quasi-optic resonator located in an oversize waveguide are presented. Structures with various shapes of the mirror are investigated. The results obtained with the help of the proposed technique are compared with the results obtained by means of an approximate approach.     

Scattering cross-section characterisation of vegetation media atmicrowave frequencies

The backscatter signal level emerging from vegetation media and its dependence on the azimuthal direction of the receiving antenna are investigated. Experimental results obtained at 11.2 GHz using two different test sites are presented and further characterised in terms of the scattering cross-section per unit area     

Determination of scattering widths of a long thin wire using an open resonator

Using an open-resonator method, the scattering widths of a set of thin copper wires have been measured. The results are in agreement with theory to within about 9%.     

Fine tuning of a millimetre-wave open resonator

The discussion is of a method of fine tuning and frequency setting of a millimetre-wave open resonator, which represents an improvement over the conventional method of tuning by moving one mirror. The important features of the mechanism are examined. A theoretical analysis of the situation supports the experimental results.